This proposal describes a five-year training program to develop an academic career in Hematology and gene therapy. The program will further advance the investigator's research skills in the development of a viral vector system for the treatment of hematopoietic disorders. The investigator will be mentored by Dr. David Russell, well recognized for his achievements in developing the adeno-associated virus (AAV) vector system for gene targeting. The research will focus on the process of the gene targeting using parvovirus vectors. Most commonly, gene therapy involves the process of gene addition, where a complete expression cassette is delivered to cells. In contrast, gene targeting uses homologous sequences to alter the cell's endogenous genes. This method can be used to either "knock out" or correct a mutated gene. An advantage over gene addition is the corrected gene will be in the proper location in the chromosome to ensure cell specific regulation. Previous work by Dr. Russell has demonstrated that AAV vectors are one of the most efficient vector systems for gene targeting. The objectives of this proposal are to improve the understanding of the mechanism of gene targeting with parvovirus vectors and to develop a parvovirus vector system for gene targeting in hematopoietic cells, a cell type poorly infected by AAV. To achieve these objectives, the investigator has developed a new vector system for gene targeting based upon another parvovirus, the minute virus of mice (MVM). MVM's property of packaging single stranded DNA of one polarity, in contrast to AAV's packaging of both strands equally, will be used to determine the molecular mechanisms of gene targeting. A MVM subtype's ability to infect cells of the hematopoietic system will be used to construct a vector to improve gene targeting in hematopoietic cells. The proposals specific aims include 1) Develop a MVM based vector system for gene targeting, 2) Determine if single stranded vectors of one polarity are sufficient for gene targeting, and 3) Demonstrate gene targeting in hematopoietic stem cells. The completion of this project and the training received at the University of Washington will prepare the principle investigator to be a leading researcher in gene therapy.